Thermal water purification processes, such as thermal desalination of salt water using multiple effect distillation (MED), use heat from a low-pressure steam energy source to effect the water purification process. Low pressure steam is generated using common boiler technology (cf. U.S. Pat. Nos. 4,338,199 and 5,441,548).
It is known to use other forms of energy for desalination. For example, U.S. Pat. No. 5,421,962 utilizes solar energy for desalination processes, U.S. Pat. Pub. 2011/0162952 utilizes energy from a gasification process, and U.S. Pat. Pub. 2011/0147195 uses waste heat from a power generation plant for the desalination process.
Hydrogen production processes, such as catalytic steam-hydrocarbon reforming, partial oxidation reforming, catalytic partial oxidation reforming, and autothermal reforming need to reject heat to the environment. Waste heat may need to be removed from an intermediate synthesis gas stream prior to separating the synthesis gas in a gas separator to form hydrogen or other hydrogen-containing product gas. Waste heat is typically rejected to the environment via an air cooler driven by a cooling fan and/or a trim cooler where cooling is provided by cooling water.
Industry desires to utilize waste heat from reforming processes. For example, catalytic steam-hydrocarbon reforming processes release a large amount of waste heat under various circumstances. One circumstance is when the energy cost is low and less capital is spent on heat recovery. Another circumstance is when the process does not produce a large amount of high pressure export steam due to the lack of demand for export steam. Low or zero export steam production reduces the heat sink for the process, resulting in a large amount of waste heat.
Industry desires to produce purified water in water-stressed regions. The water can be used as make-up water in the catalytic steam-hydrocarbon reforming process, making the process self-sufficient with regard to water. Water can also be sold as a product for industrial and municipal use.
Industry desires to reduce or eliminate water treatment cost in a catalytic steam-hydrocarbon reforming plant. Currently, make-up water needs to be treated in a catalytic steam-hydrocarbon reforming plant so that it meets the requirements for the boiler feed water. These treatments include filtration to remove particulates, demineralization to remove minerals, and deaeration to remove soluble gases such as O2 and CO2.
Industry desires to reduce the capital and energy cost of reforming processes. The thermal efficiency of reforming processes depends on the utilization of low level heat. When the energy cost is high, more low level heat is recovered for better thermal efficiency or lower energy cost. However, recovering more heat means using more and/or larger heat exchangers, resulting in higher capital cost. In contrast, when the energy cost is low, the capital cost for heat exchangers is minimized with the sacrifice of thermal efficiency or energy cost.
There exists a need in the art for systems and processes for producing H2-containing product gas and purified water that are cost-effective and provide greater utilization of waste heat from catalytic steam-hydrocarbon reforming processes.